Greetings in the markets. They loved to be denoted as superiors by respectful salutations in public places. To be called Rabbi, Rabbi; "My Master" (compare the French Monsieur, used not only vocatively, but absolutely); the term addressed by scholars to their teacher, and repeated for ostentation's sake, of course implying superiority in those thus called.
Christ himself was thus addressed by those who desired to denote his authority and preeminence (Matthew 22:16, Matthew 22:24, Matthew 22:36; comp. John 1:38). These greetings and salutations were enjoined on scholars and inferiors, under pain of ecclesiastical censure and loss of salvation.